cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A251660 Table of coefficients in functions R(n,x) defined by R(n,x) = exp( n*x*G(n,x)^(n-1) ) / G(n,x)^(n-1) where G(n,x) = 1 + x*G(n,x)^n, for rows n>=1.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 8, 1, 1, 1, 4, 21, 56, 1, 1, 1, 5, 40, 261, 592, 1, 1, 1, 6, 65, 712, 4833, 8512, 1, 1, 1, 7, 96, 1505, 18784, 120303, 155584, 1, 1, 1, 8, 133, 2736, 51505, 663424, 3778029, 3456896, 1, 1, 1, 9, 176, 4501, 115056, 2354725, 29480896, 143531433, 90501632, 1
Offset: 1

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Author

Paul D. Hanna, Dec 21 2014

Keywords

Examples

			This table begins:
n=1: [1, 1,  1,   1,     1,       1,        1,           1, ...];
n=2: [1, 1,  2,   8,    56,     592,     8512,      155584, ...];
n=3: [1, 1,  3,  21,   261,    4833,   120303,     3778029, ...];
n=4: [1, 1,  4,  40,   712,   18784,   663424,    29480896, ...];
n=5: [1, 1,  5,  65,  1505,   51505,  2354725,   135258625, ...];
n=6: [1, 1,  6,  96,  2736,  115056,  6455376,   454666176, ...];
n=7: [1, 1,  7, 133,  4501,  224497, 14926387,  1245099709, ...];
n=8: [1, 1,  8, 176,  6896,  397888, 30584128,  2948178304, ...];
n=9: [1, 1,  9, 225, 10017,  656289, 57255849,  6262226721, ...];
n=10:[1, 1, 10, 280, 13960, 1023760, 99935200, 12226859200, ...]; ...
where e.g.f. of row n equals: exp( n*x*G(n,x)^(n-1) ) / G(n,x)^(n-1).
Related table of coefficients in G(n,x) = 1 + x*G(n,x)^n  begins:
n=1: [1, 1,  1,   1,    1,     1,      1,        1, ...];
n=2: [1, 1,  2,   5,   14,    42,    132,      429, ...];
n=3: [1, 1,  3,  12,   55,   273,   1428,     7752, ...];
n=4: [1, 1,  4,  22,  140,   969,   7084,    53820, ...];
n=5: [1, 1,  5,  35,  285,  2530,  23751,   231880, ...];
n=6: [1, 1,  6,  51,  506,  5481,  62832,   749398, ...];
n=7: [1, 1,  7,  70,  819, 10472, 141778 , 1997688, ...];
n=8: [1, 1,  8,  92, 1240, 18278, 285384,  4638348, ...];
n=9: [1, 1,  9, 117, 1785, 29799, 527085,  9706503, ...];
n=10:[1, 1, 10, 145, 2470, 46060, 910252, 18730855, ...]; ...
		

Crossrefs

Programs

  • PARI
    {T(n,k)=local(G=1); for(i=0, k, G=1+x*G^n +x*O(x^k)); k!*polcoeff(exp(n*x*G^(n-1))/G^(n-1), k)}
    /* Print as a rectangular table */
    for(n=1, 10, for(k=0,10, print1(T(n,k), ", "));print(""))
    /* Print as a flattened table */
    for(n=0, 12, for(k=0,n, print1(T(n-k+1,k), ", "));)
    /* Print the Related table of functions G(n,x) = 1 + x*G(n,x)^n */
    {R(n,k)=local(G=1); for(i=0, k, G=1+x*G^n +x*O(x^k)); polcoeff(G, k)}
    for(n=1, 10, for(k=0,10, print1(R(n,k), ", "));print(""))
    
  • PARI
    /* Binomial sum formula for term T(n,k) */
    {T(n,k) = if(k<=1,1,sum(j=0,k, n^j * k!/j! * binomial(n*(k-1)-j, k-j) * (j-1)/(k-1)))}
    for(n=1, 10, for(k=0, 10, print1(T(n, k), ", ")); print(""))

Formula

E.g.f. of row n, R(n,x), for n>=1, satisfies:
(1) [x^k/k!] R(n,x)^(k+1) = n^(k-1) * (n+k) * (k+1)^(k-2) for k>=0.
(2) R(n,x) = exp( n*x*G(n,x)^(n-1) ) / G(n,x)^(n-1), where G(n,x) = 1 + x*G(n,x)^n.
(3) R'(n,x)/R(n,x) = G(n,x)^(n-1), where G(n,x) = 1 + x*G(n,x)^n.
T(n,k) = Sum_{j=0..k} n^j * k!/j! * binomial(n*(k-1)-j, k-j) * (j-1)/(k-1) for k>1, n>=1.

A380603 Expansion of e.g.f. exp(2*x*G(x)^2) where G(x) = 1 + x*G(x)^3 is the g.f. of A001764.

Original entry on oeis.org

1, 2, 12, 140, 2512, 61392, 1905184, 71781824, 3183563520, 162497556224, 9383803201024, 604888546242048, 43056560538093568, 3354362248463544320, 283895464602180231168, 25938521255822517813248, 2544584391277895815069696, 266765818037212169468706816, 29764238411096397030375424000
Offset: 0

Views

Author

Seiichi Manyama, Jan 28 2025

Keywords

Crossrefs

Programs

  • PARI
    a(n) = if(n==0, 1, 2*n!*sum(k=0, n-1, 2^(n-k)*binomial(2*n+k, k)/((2*n+k)*(n-k-1)!)));

Formula

E.g.f.: B(x)^2, where B(x) is the e.g.f. of A380511.
a(n) = 2 * n! * Sum_{k=0..n-1} 2^(n-k) * binomial(2*n+k,k)/((2*n+k) * (n-k-1)!) for n > 0.
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